This invention relates to the polymerization of olefins. In another aspect, this invention relates to a novel catalyst system useful for the polymerization of 1-olefins, especially for the production of ethylene polymers. In accordance with another aspect, this invention relates to a method of preparing a titanium-containing composition associated with a chemically treated particulate silica-containing composition and a dihydrocarbylmagnesium useful as a catalyst component for the polymerization of 1-olefins. In a further aspect, this invention relates to a process for the polymerization of olefins in the presence of a catalyst comprising a catalyst component (A) which is obtained as the at least partially milled product of a mixture of at least two different silica-containing materials in which at least one silica has been chemically treated, a dihydrocarbylmagnesium compound and a halogenated tetravalent titanium compound, and a cocatalyst component (B) comprising an organoaluminum compound. In another aspect, this invention relates to the use of a milled blend of silica-containing materials having widely different MI (polymer melt index) responses in which at least one of the silica-containing materials has been chemically treated so that an ethylene polymer of broad molecular weight distribution is obtained when a silica blend is used with a dihydrocarbylmagnesium compound, a halogenated tetravalent titanium compound and an organoaluminum cocatalyst (Component B).
It is known to polymerize 1-olefins and mixtures thereof in the presence of organometallic catalyst systems in a low pressure process. The activity of an olefin polymerization catalyst is one important factor in a continuous search for a catalyst useful for the polymerization of 1-olefins. It is also desirable that the process used in forming the catalyst be such as to allow ease in preparation and to allow control over the final catalyst formed. In addition, it is desirable in some instances to provide a catalyst for effecting the polymerization of olefins to polymers of broad molecular weight distribution.
The present invention is based upon the discovery that a catalyst having quite different properties is obtained if a milled mixture of different silica-containing supports having different physical properties, a dihydrocarbylmagnesium compound, and a titanium tetravalent halogenated compound is used as a catalyst component in the production of ethylene polymers. The ethylene polymers formed according to the invention exhibit broad melt index and broad molecular weight distributions.
Accordingly an object of this invention is to provide an improved process for the polymerization of 1-olefins.
Another object of this invention is to provide a novel and improved catalyst.
Another object of this invention is to provide a two-component catalyst system effected for the polymeization of 1-olefins.
A further object of this invention is to provide a process for the production of ethylene polymers having broad molecular weight distribution.
Other objects, aspects and the several advantages of this invention will become apparent to one skilled in the art upon reading this specification and the appended claims.